1. Field of the Invention
The present invention relates to a method of rapidly reworking color filters, and more particularly, to a method of completely removing non-polar R/G/B colorants of a color filter array by utilizing a PAD-PI type negative photoresist, plasma clean process and solvent clean process.
2. Description of the Prior Art
A charge-coupled device (CCD) is an optical electronic device used to transform light into an electronic signal. Applications of the charge-coupled device include monitors, transcription machines and cameras etc. However, due to high cost and large dimensions of the charge-coupled device, there are limitations in applications of the charge-coupled device. To overcome the above mentioned drawbacks, a CMOS photodiode is therefore produced. Because the CMOS photodiode is produced by utilizing traditional semiconductor fabrication, the dimensions and production cost of the CMOS photodiode are reduced. Additionally, the CMOS photodiode can be applied in personal computer cameras and digital cameras.
Whether image sensing equipment is composed of a CCD or a CMOS photodiode, incident light must be divided into a combination of rays with different wavelengths, such as red light, blue light and green light. For example, yellow light can be divided into a combination of 50% blue light and 50% green light. As a result, an optical sensing device needs a filtering array to divide incident light. A color filter is made of a photosensitive resin and is patterned by utilizing a photolithography process and an etching process. Then, the color filter is colored by dyes. Directly utilizing a photoresist containing dyes may also serve as the color filter.
As errors occur in fabricating a color filter array, the color filter array needs to be removed completely. Usually, the color filter array is removed by utilizing a plasma cleaning process. However, after the color filter array is aligned in a photolithography process, molecules of dyes in the color filter array perpetrate a cross-linking reaction to form polymers with larger molecular weight. As a result, the color filter array cannot be removed completely by utilizing the plasma cleaning process.
In general, a positive photoresist is removed by utilizing solutions composed of N-methyl-2pyrrolidone (NMP) and acetone, or by utilizing the plasma cleaning process and a solvent cleaning process. Before the color filter array is aligned in a photolithographic process, the color filter array can be removed completely by a color filter array (CFA) development solution. However, after the color filter array is aligned in a photolithographic process, the color filter array cannot be removed completely by the CFA development solution. The color filter array is a negative photoresist, which contributes to a cross-linking reaction in an exposing process. The cross-linked color filter array cannot be removed completely by utilizing the NMP solution, the development solution and the plasma ash cleaning process. As a result, it is necessary to develop a method of completely removing the cross-linked color filter array.
It is therefore a primary objective of the present invention to provide a method of rapidly removing non-polar R/G/B colorants of a color filter array.
In a preferred embodiment, the present invention provides a method to remove a color filter array rapidly. The color filter array composed of non-polar colorants is formed on a silicon nitride layer. A cracking pre-treatment is performed to decompose cross-linked polymers in the non-polar R/G/B colorants into small molecules. A plasma ash cleaning process is performed subsequently in order to oxidize the non-polar R/G/B colorants. Then, a solvent cleaning process is performed.
It is an advantage of the present invention that a cracking pre-treatment is utilized to decompose the cross-linked polymers in the non-polar R/G/B colorants into small molecules. The cracking pre-treatment utilizes a PAD-PI development solution, which is a negative photoresist development solution comprising methoxy-2-propyl-acetate. The PAD-PI development solution can effectively decompose cross-linked polymers into small molecules, which can be removed by a plasma ash cleaning process and a solvent cleaning process.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.